Method and apparatus for drying fibrous material

ABSTRACT

A method and apparatus for drying two separate units of moist fibrous material. The method includes the steps of flowing a gaseous medium through both units of material in a closed system in such a way that the gaseous exhaust from one unit is the gaseous intake of the other unit, heating the gaseous medium subsequent to its passage through each unit of material and removing moisture from the gaseous medium after passage through the unit of material. The apparatus includes two closed containers each of which has a support for the material which when having material thereon divides the interior of the container into an outer chamber and an inner chamber, a circulation system serially interconnecting the containers by connecting the inner chambers of the containers to each other and connecting the outer chambers of the containers to each other and containing a pump and a heat exchanger interposed in the system before each container. A condenser also may be included in the system to remove moisture.

United States Patent [191 Karreret al.

[ Dec. 23, 1975 METHOD AND APPARATUS FOR DRYING Primary ExaminerKenneth W. Sprague FIBROUS MATERIAL Assistant ExaminerJames C. Yeung Attorney, Agent, or FirmStevens, Davis, Miller & [75] Inventors: Friedrich Wilhelm Johann Karrer, v Mosher Stockholm; Per Gustaf Mellgren, Vaxjo, both of Sweden [57] ABSTRACT A method and apparatus for drying two separate units [73] Asslgnee' KaFrer System zolhkon of moist fibrous material. The method includes the Swltzerland steps of flowing a gaseous medium through both units of material in a closed system in such a way that the [22] F'led: 1974 gaseous exhaust from one unit is the gaseous intake of the other unit, heating the gaseous medium subse- [211 Appl' N05 514,774 quent to its passage through each unit of material and removing moisture from the gaseous medium after passage through the unit of material. The apparatus [52] US. Cl. 34/20; 34/77; 34/104; includes two closed containers each of which has a 2 34/212 support for the material which when having material [51] Int. Cl. F26B 23/00 thereon divides the interior of the container into an [58] new of Search 34/19 21, 54, outer chamber and an inner chamber, a circulation 34/103 77 78 209-213 225; system serially interconnecting the containers by con- 68/20 189 necting the inner chambers of the containers to each other and connecting the outer chambers of the con- [56] References Ci d tainers to each other and containing a pump and a UNITED STATES PATENTS heat exchanger interposed in the system before each 1997 380 4/1935 H b kl et al 34/21 container. A condenser also may be included in the OlTl UC 6 2,321,541 6/1943 Bergmann et al System to remove molsture' 3,631,691 1/1972 Karrer et al. 68/20 6 Claims, 1 Drawing Figure i 5 l l 2 I I I 7 77a 24 1 ,3 H llb V V L 72b 17 v 1 a V 15 3 The present invention relates to a method and an apparatus for drying fibrous material, and in particular fibrous material in the form of reels of yarn.

More specifically the invention relates to the drying of fibrous material in apparatus of the type in which said material is arranged in a container in a manner such that there are formed in the container two chambers which are interconnected solely through the medium of said material, and in which a stream of gaseous medium (air or steam or a mixture of air and steam) is passed through said material in order to heat and/or dry the same. With this kind of drying method channels often form in said material, expecially when the material is in the form of large reels of yarn, so that towards the latter stages of a drying and/or heating process only a relatively small portion of air isable to pass through the wet layers of material, whereby the process is slowed down.

An object of the present invention is to improve upon the aforementioned material drying method. The advantages afforded by the method of the present invention over the known methods include a more uniform drying of the material being treated and a gentler drying of said material as a result of a smaller temperature gradient therethrough, and a lower consumption of power and steam. In addition hereto the apparatus with which the method is effected is simpler to operate than the prior art apparatus.

The method of the present invention is mainly characterized by the fact that there are used two containers of the aforementioned type and that during at least a part of the material drying process gaseous medium is caused to flow circulatory in series through the material being heated in both containers while heating said medium prior to its entry into each of said containers.

According to one embodiment of the invention the circulation of gaseous medium is effected by means of a vacuum pump, the suction side of which is connected to a first chamber of a first container, so that said first chamber is placed under a slight vacuum, while the pressure side of the pump is connected to a corresponding chamber of a second container, so that said corresponding chamber is placed under a slight overpressure which is equalized in a second chamber of said second container by suction from the first container. After a certain period of time, the direction of flow of said gaseous medium is reversed, so that the material in the two containers is subjected to alternating flow directions of said medium, by means of a single vacuum pump.

By using two containers connected in series in the aforedescribed manner, the path travelled by the circu lating medium per cycle through the material being treated is doubled, thereby utilizing the heat transferring ability of the gaseous medium to a corresponding degree. By reversing the direction of flow of the gaseous medium there is obtained as a result of the ensuing alternating diffusion drying process a moisture equalization effect. This equalization effect results in a saving of heat and power. When using a vacuum pump arranged to provide a pressure difference of, for example, 0.7 bars, it is possible to maintain passage of the gaseous medium through two layers of the material to be treated per cycle of medium flow whilst consuming 2 approximately the same amount of energy as that required to pass the medium through one layer. This is also true in the case of large reels of yarn.

An' embodiment of an apparatus for putting the method of the invention into effect is shown diagrammatically in the accompanying drawing. The illustrated apparatus comprises two containers 1 and 2 of identical construction. In the lower portion of the container 1 there is arranged an inner chamber 3 which is adapted to carry perforated pipes 4, said pipes being arranged to accommodate material to be treated in the form of reels of yarn, as indicated at 5, so that the chamber 3 is in communication with an outer chamber 6 located around the reels 5, solely through said reels, via the perforations in the pipes 4. Extending from the inner chamber 3 through the wall of the container 1 is a connection stub 7, while a similar connection stub 8 provides for communiciation with the outer chamber 6. The container 2 is of the same construction as the container 1, the corresponding connection stubs in said container 2 being identified by the references 9 and 10. The two stubs 8 and 10 extending to respective outer chambers are joined together by means of a line 11 in which there is arranged a heat exchanger 13 and two valves 11 a, 11b. The two stubs 7 and 9 extending to respective inner chambers are joined together by means of two parallel lines 12a, 12b in which there are arranged valves 14, 16 and l5, 17 respectively. The suction side of a vacuum pump 18 is connected to the line 12b between the valves 15 and 17, while the pressure side of said pump is connected to the line 12a between the valves 14 and 16 via a condensor 19 and a heat exchanger 20. An outlet line 21 having a valve 22 is connected to the outlet side of the condensor l9 and a valve 23 is arranged in the connection between the condensor and the line 12a so that by adjusting the valves 22 and 23, the pressure side of the pump 18 can be made to communicate either with atmosphere through the line 21 or with the line 12a. The suction side of the pump can be made to communicate with the inner chambers of the containers 1 and 2, either singly or together, via the valves 15 and 17. The pressure side of the pump 18 can also be made to communicate with the inner chamber of one or both of the containers 1 and 2.

Connected to the line 11 is a further line 24 having a valve 25 which can be made to communicate with the atmosphere. A steam source 28 is connected to the line 24 via a valve 27 so that air or steam, or a mixture of steam and air, can be passed through the line 24.

When drying material located in the containers 1 and 2, it is suitable to first dewater said material mechanically, by causing to flow therethrough air or steam or a mixture of air and steam, as disclosed for example in the Swedish Patent Specification No. 328 842. To this end, the suction side of the vacuum pump can be connected to the inner chambers of both containers 1 and 2, by opening the valves 15 and 17, with the valves 14 and 16 closed. The valve 22 is opened and the valve 23 is closed, while the valves 11a, 11b are opened and the line 24 is connected to atmosphere or to the steam source 28 or to both by means of the valves 25, 27. Subsequent to this mechanical dewatering process, the actual material drying process is effected, in which process the valve 22 is closed and the valve 23 opened and, for example, the valves 14 and 17 are opened and the valves 15 and 16 closed. The valve 25 is held open so that the line 24 is connected to atmosphere, but the 3 connection to the steam source is closed. Thus, the vacuum pump draws in the container 2 air from the outer to the inner chamber through the material located in said container, whereupon moisture contained by the material is absorbed by the air passing therethrough. This moisture is condensed in the condensor 19 prior to the air being passed to the inner chamber 3 of the container 1 at a slight overpressure, said air passing through the material located in said container 1 from the inner container 3 outwardly and subsequently enters the outer chamber of the container 2. Prior to its entry into either of the containers 1 and 2, the air is pre-heated by the heat exchangers 13 and 20. After a certain period of circulation in one direction, the setting of the valves l4, l5, l6 and 17 is reversed, thereby reversing the direction of flow of the air, so that said air passes from within and outwardly through the material in the container 2 and in the opposite direction in the container 1. This reversal in the flow direction affords substantial equalization of the moisture in said material, and therewith a more uniform drying thereof.

The introductory mechanical dewatering process can also be cycled in the manner just described. It is also possible to carry out said dewatering process in individual chambers per se., the containers in which said process as not in effect being disconnected by means of the valves 11a or 11b.

We claim:

1. An apparatus for drying fibrous material, comprising two closed containers each of which has a support for said fibrous material to be dried, said material being positioned on said support in a manner such as to divide the interior of each container into an inner and an outer chamber which communicate with each other solely via said material, a circulation system for serially interconnecting said containers by connecting said inner chambers to each other and said outer chambers to each other and containing a pump and a heat exchanger arranged in said circulation system in front of each container.

2. The apparatus according to claim 1 including one of said heat exchanges connected in the connection between the outer chambers of the two containers.

3. The apparatus according to claim 1 including a condenser connected between the pressure side of the pump and the corresponding container, said pump being a vacuum pump.

4. The apparatus according to claim 3, including means for reversing the connection of the pressure and suction sides of the vacuum pump to the inner chambers of the two containers.

5. A method for drying two separate units of moist fibrous material, especially in the form of reels of yarn, comprising flowing in a closed circuit a gaseous medium through both units of material, such that the gaseous exhaust from one unit is the gaseous intake of said other unit, heating said gaseous medium subsequent to its passage through each unit of said material and removing moisture from said gaseous medium in said closed circuit.

6. The method according to claim 5, including reversing the direction of flow of the gaseous medium at least once during the circulation and wherein the gaseous medium is passed in opposite directions through the units of material. 

1. An apparatus for drying fibrous material, comprising two closed containers each of which has a support for said fibrous material to be dried, said material being positioned on said support in a manner such as to divide the interior of each container into an inner and an outer chamber which communicate with each other solely via said material, a circulation system for serially interconnecting said containers by connecting said inner chambers to each other and said outer chambers to each other and containing a pump and a heat exchanger arranged in said circulation system in front of each container.
 2. The apparatus according to claim 1 including one of said heat exchanges connected in the connection between the outer chambers of the two containers.
 3. The apparatus according to claim 1 including a condenser connected between the pressure side of the pump and the corresponding container, said pump being a vacuum pump.
 4. The apparatus according to claim 3, including means for reversing the connection of the pressure and suction sides of the vacuum pump to the inner chambers of the two containers.
 5. A method for drying two separate units of moist fibrous material, especially in the form of reels of yarn, comprising flowing in a closed circuit a gaseous medium through both units of material, such that the gaseous exhaust from one unit is the gaseous intake of said other unit, heating said gaseous medium subsequent to its passage through each unit of said material and removing moisture from said gaseous medium in said closed circuit.
 6. The method according to claim 5, including reversing the direction of flow of the gaseous medium at least once during the circulation and wherein the gaseous medium is passed in opposite directions through the units of material. 